当前，我国的安全面临着极为严峻的挑战。我们既要对付现实的和潜在的武力威胁，又要警惕敌对势力的"和平演变"阴谋，防止渗透和颠覆。
参考答案：对
--- Could you tell me what he said just now?
--- Sorry, I ______ what was going on outside.
A．had thought
B．was thinking
C．thought
D．think
喷射砼时的（）顺序是先墙后拱，先下后上，先凹后凸，先裂隙后表面。
